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US strategy for using weight of evidence in risk assessment

General - River © Dmitry Naumov -

There is a general lack of practical guidance for weight of evidence (WOE) approaches to predictive ecological risk assessments, particularly for regulatory purposes, according to a US study published in the journal Human and Ecological Risk Assessment.

Bruce Hope, principal environmental scientist at consultancy CH2M HILL in Oregon, and Jacquelyn Clarkson from Environ in Louisiana worked under contract to the US Environmental Protection Agency (EPA) to assess global WOE approaches to environmental risk assessment, in part through a literature review.

In particular, the scientists found that many of the WOE strategies are so complex that they are impractical for regulatory use. They also found that WOE approaches are most commonly used in causal assessments, to pick out chemical culprits for past events. In the US, what has been packaged as risk assessment frequently asks if a chemical has caused a particular problem, said lead author Dr Hope. “There is very little out there where people are thinking of WOE from a true risk assessment perspective, predicting the future,” he added.

The two scientists have suggested a WOE strategy based on their findings. “Our approach is a simplification of other people’s approaches,” said Dr Hope. “The real goal was to make it consistent with the US ecological risk assessment framework.”

Dr Hope thinks that the EPA will at some stage want to go down the WOE route for ecological assessments. In the meantime he hopes that his document will serve as background material to aid the EPA’s Risk Assessment Forum in putting together draft guidance.

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